In auto-laundries, otherwise known as car washes, it is known to use endless chain conveyors of the type having “dollies” linked into the chain at regular intervals. The dollies are used to push vehicles along the conveyor by engaging the tread surface of a tire. To function properly dollies must have tire engaging rollers and track engaging rollers. Typically the tire engaging rollers are larger in diameter than the track engaging rollers and are disposed in a center slot between opposite longitudinally extending track rails. The dollies include an axle member on which the rollers are mounted. Dollies are connected into the continuous loop chain by means of a center link which may be mounted on the axle.
The track structure which is used in combination with the chain and the dollies typically comprises three separate tracks mounted in parallel and at different levels. The top track accommodates the tire of the vehicle being laundered and also provides the travel path for dollies which are selected at any given time. An intermediate level track provides the forward track for unselected dollies and the bottom level track provides a return path. A selector is used to transfer dollies from the intermediate to the top level tracks when a vehicle is present to be conveyed.
It is desirable to have the gap between the parallel rails as small as possible. A practical limit of about two or three inches is imposed by the need to have tire engaging rollers make stable contact with the vehicle tire when pushing a vehicle along the conveyor.
Belanger, Inc., assignee of the present invention, has for many years utilized a novel dolly design using rollers which engage both the top and bottom surfaces of the track. See U.S. Pat. No. 4,715,287 “Vehicle Conveyor and Wheel Engaging Dolly,” issued Dec. 29, 1987. This dolly permits the use of a fairly narrow slot while maintaining stability in the engagement between the dollies and the tires of vehicles being conveyed.
Another problem associated with slotted track auto-laundry conveyors arises out of the fact that dirt and debris falls through the slot and collects in the track structure. The track rails are usually made from L-shaped angle irons and this provides corners which collect dirt. After a while, accumulated dirt can interfere with the proper contact of the track engaging rollers with the intermediate and lower tracks. This in turn causes unusual roller wear which interferes with proper operation of the conveyor.
Another problem associated with auto-laundry conveyors of conventional design arises out of the design of the guard rails which are used to maintain the tires of a vehicle being conveyed on the track; i.e., many vehicles have worn tires or wheels that are out of alignment and these vehicles tend to veer off center and try on their own to exit the track. A guard rail must be designed in such a way as to turn vehicles back onto the track and to prevent the side wall of the tire from climbing over the guard rail and exiting the track. However, the guard rail should be designed to avoid damaging the wheels of the vehicles being conveyed.
Still another problem arises in the use, installation and operation of conventional auto-laundry conveyors in that the conveyors are typically constructed in a modular fashion using pieces of constant length, typically 10 feet, to construct conveyor tracks of varying length. The entry and exit sections tend to become heavy because they include additional components: the exit section typically comprises a drive motor and the entry section typically comprises a dolly selector and a take-up mechanism all of which add weight to these sections making it difficult to handle them during the installation and/or replacement phases.